MoveAlongSpline.cs

#pragma warning disable 0649

using UnityEngine;
using UnityEngine.U2D;

public class MoveAlongSpline : MonoBehaviour
{
    [SerializeField] private float _speed = 1.0f;
    [SerializeField] private SpriteShapeController _spriteShapeController;

    private Vector3[] _positions;
    private LTDescr _tween;

    private void Start()
    {
        Debug.Assert(transform.parent == _spriteShapeController.transform, $"Please make {name} a direct child of {_spriteShapeController}", gameObject);
        Spline spline = _spriteShapeController.spline;
        int bezierCount = spline.GetPointCount() - 1;
        _positions = new Vector3[bezierCount * 4];
        for (int i = 0; i < bezierCount; ++i)
        {
            // Get points in local space
            Vector2 startPoint = _spriteShapeController.spline.GetPosition(i);
            Vector2 startControl = startPoint + (Vector2)_spriteShapeController.spline.GetRightTangent(i);
            Vector2 endPoint = _spriteShapeController.spline.GetPosition(i + 1);
            Vector2 endControl = endPoint + (Vector2)_spriteShapeController.spline.GetLeftTangent(i + 1);

            // Note: the control for the end and start are reversed! This is just a quirk of the LeanTween API.
            _positions[4 * i + 0] = startPoint;
            _positions[4 * i + 1] = endControl;
            _positions[4 * i + 2] = startControl;
            _positions[4 * i + 3] = endPoint;
        }

        // Start the tween, you can control it (e.g. pause, resume) using this handle
        _tween = LeanTween.moveLocal(gameObject, _positions, 0.0f)
            .setLoopPingPong()
            .setEase(LeanTweenType.easeInOutQuad)
            .setSpeed(_speed)
            .setPassed(Time.time);
    }
}